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Human A&P BIO 304 · American River College ← Course home (Week 7)

BIO 304 . WEEK 7 . THURSDAY . LAB WORKBOOK

Gas Exchange and Transport

External and internal respiration; how O2 and CO2 ride the bloodstream.

Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.

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Part 1 of 2

Anatomy Lab

1A. What you will draw

Gas exchange happens twice in every breath cycle: at the alveoli (external respiration, lungs pick up O2 and drop CO2) and at the tissues (internal respiration, tissues pick up O2 and dump CO2). Draw both interfaces and how hemoglobin transports the load.

Box A. Alveolus and tissue gas exchange

Directions

  1. Draw two panels side by side: the alveolus (LEFT) and a body tissue (RIGHT).
  2. Left panel: an alveolus with air inside. PO2 in alveolus is about 104 mmHg, PCO2 is about 40 mmHg. Wrap the alveolus with a pulmonary capillary. Blood entering the capillary has PO2 about 40, PCO2 about 45. Show O2 diffusing INTO the blood and CO2 diffusing OUT to the alveolus. By the time blood leaves, PO2 is ~100 and PCO2 is ~40.
  3. Right panel: a tissue cell. Inside the cell, PO2 is about 40 and PCO2 is about 45 (because the cell is consuming O2 and making CO2). Wrap the tissue with a systemic capillary. Blood entering has PO2 ~100, PCO2 ~40. Show O2 diffusing INTO the tissue and CO2 diffusing OUT to the blood. By the time blood leaves, PO2 is ~40, PCO2 is ~45.
  4. Add labels: external respiration (lungs), internal respiration (tissues). Note: diffusion goes down partial pressure gradients.

Box B. Hemoglobin transports O2

Directions

  1. Draw a hemoglobin molecule schematically: four globin chains (subunits) clustered, each containing a heme group with a central iron (Fe). Label one heme.
  2. Show the hemoglobin in two states: deoxyhemoglobin (no O2 bound) and oxyhemoglobin (4 O2 molecules bound, one per heme).
  3. Draw a hemoglobin LOADING in the pulmonary capillary (high PO2): O2 binds.
  4. Draw a hemoglobin UNLOADING in a tissue capillary (low PO2): O2 dissociates.
  5. Note: hemoglobin shows cooperative binding (first O2 makes the next easier to bind), producing the S-shaped saturation curve.
  6. Below, note three factors that promote unloading: low pH, high PCO2, high temperature (the Bohr effect). These are all features of active tissue.

1C. Structures to label (13)

After you finish each drawing, label every structure below directly on your sketch.

  1. Alveolus
  2. Pulmonary capillary
  3. PO2 (high in alveolus, low in tissue)
  4. PCO2 (low in alveolus, high in tissue)
  5. External respiration
  6. Internal respiration
  7. Hemoglobin
  8. Globin chain
  9. Heme group
  10. Iron (Fe)
  11. Oxyhemoglobin
  12. Deoxyhemoglobin
  13. Bohr effect

Part 2 of 2

Physiology Lab

2A. Oxygen-hemoglobin dissociation curve

Sketch the oxygen-hemoglobin dissociation curve on a graph. x-axis: PO2 (0 to 100 mmHg). y-axis: percent hemoglobin saturation (0 to 100). Then answer the questions below.

1. At PO2 = 100 mmHg (lung capillary), what is hemoglobin saturation?
2. At PO2 = 40 mmHg (tissue capillary at rest), what is saturation?
3. Why is the curve S-shaped (sigmoidal) rather than linear?
4. Predict the direction the curve SHIFTS when blood pH drops, PCO2 rises, or temperature rises. What does the shift accomplish at the tissue?
5. A patient is given high-FiO2 oxygen therapy, raising arterial PO2 from 100 to 200 mmHg. Predict the change in hemoglobin saturation (it doesn't double).

2B. Synthesis questions

Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.

1. Carbon monoxide (CO) binds hemoglobin with about 200 times the affinity of O2 and forms carboxyhemoglobin. Predict the effects on (a) hemoglobin saturation, (b) the dissociation curve, (c) O2 delivery to tissues. Why is CO poisoning so dangerous even at low concentrations?
2. Most CO2 in the blood is transported as bicarbonate (HCO3-), formed inside red blood cells by carbonic anhydrase. Trace this pathway: CO2 enters the RBC, becomes carbonic acid, then dissociates. Where does the H+ go, and where does HCO3- go?
3. An athlete in heavy exercise has muscle PCO2 high, pH low, and temperature elevated. Predict (using the Bohr effect) what happens to hemoglobin's affinity for O2 at the muscle, and why this is exactly what the muscle needs.

3. What to submit

Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.